Apparatus and method for adding synchronization information to an auxiliary data space in a video signal and synchronizing a video

ABSTRACT

A video synchronization apparatus and method by adding sync data to an ancillary data space of a video signal are provided. A sync data adding apparatus may include a sync data generator to generate sync data; and a sync data adder to add the sync data to an ancillary data space of a video signal.

TECHNICAL FIELD

The present invention relates to a video synchronization apparatus andmethod by adding synchronization data (sync data) to an ancillary dataspace of a video signal, and more particularly, to a sync data addingapparatus and method in which a decoding apparatus may synchronizeimages corresponding to a video signal without a need to transmit aseparate synchronization signal, or to perform a separatesynchronization process by adding sync data to an ancillary data spaceincluded in a video signal.

BACKGROUND ART

When storing or encoding and decoding a plurality of related images suchas a three-dimensional (3D) image, a free view image, a multi-viewimage, and images obtained by dividing a super resolution imagecorresponding to four to 16 folds of a high-definition (HD) class basedon an HD class and the like, the related images may need to besynchronized based on a frame unit. Accordingly, when obtaining aplurality of related images, a gen-lock technology of unifyingsynchronization signals of the respective equipment and therebysynchronizing images output from the respective equipment by connectinga synchronization signal output from a separate synchronization signalgenerator to equipment associated with an image has been employed.

However, the gen-lock technology synchronizes a plurality of pieces ofequipment and thus, may not be applicable when sequentially encoding aplurality of images using a single encoding apparatus.

Also, when encoding a plurality of images using a plurality of encodingapparatuses that employs different standards, a synchronization signalmay not be exchanged between the plurality of encoding apparatuses andthus, it may be impossible to perform a synchronization using gen-lock.

Accordingly, there is a desire for a method that may synchronize imageseven though image synchronization using gen-lock is impossible.

DISCLOSURE OF INVENTION Technical Goals

An aspect of the present invention provides an apparatus and method inwhich a decoding apparatus may synchronize images corresponding to avideo signal without a need to transmit a separate synchronizationsignal, or to perform a separate synchronization process.

Another aspect of the present invention provides an apparatus and methodthat enables a terminal receiving bitstreams to synchronize and playback the bitstreams without a need to synchronize and thereby multiplexthe bitstreams.

Another aspect of the present invention also provides an apparatus andmethod that may perform synchronization even though bitstreams to besynchronized are not received at the same time.

Technical Solutions

According to an aspect of the present invention, there is provided anapparatus for adding synchronization data (sync data), the apparatusincluding: a sync data generator to generate sync data; and a sync dataadder to add the sync data to an ancillary data space of a video signal.

According to another aspect of the present invention, there is providedan encoding system, including: a sync data adding apparatus to add syncdata to an ancillary data space of a video signal; and an encodingapparatus to generate a bitstream in which the sync data is added byencoding the video signal in which the synch data is added.

The encoding apparatus may identify the sync data in the ancillary dataspace of the video signal, and may add the identified sync data to auser data syntax among syntaxes of the bitstream.

The encoding system may further include a multiplexing apparatus tosynchronize a plurality of bitstreams based on the sync data included inthe bitstream, and multiplexes the synchronized bitstreams.

The multiplexing apparatus may determine an interval for verifying thesync data based on the user data syntax added with the sync data, andmay synchronize the plurality of bitstreams by verifying the sync dataat the determined intervals.

According to still another aspect of the present invention, there isprovided an encoding system, including: a caption data adding apparatusto add, to an ancillary data space of a video signal, caption data thatincludes sync data; an encoding apparatus to generate a bitstream byencoding the video signal in which the caption data is added; and amultiplexing apparatus to synchronize and thereby multiplex a pluralityof bitstreams based on the sync data included in the caption data of thebitstream.

The encoding apparatus may identify the sync data included in thecaption data, and may add the identified sync data to a syntaxassociated with the caption data in the bitstream.

According to yet another aspect of the present invention, there isprovided a method of adding sync data, the method including: generatingsync data; and adding the sync data to an ancillary data space of avideo signal.

According to a further another aspect of the present invention, there isprovided an encoding method, including: adding sync data to an ancillarydata space of a video signal; and generating a bitstream in which thesync data is added by encoding the video signal in which the synch datais added.

According to still another aspect of the present invention, there isprovided an encoding method, including: adding, to an ancillary dataspace of a video signal, caption data that includes sync data;generating a bitstream by encoding the video signal in which the captiondata is added; and synchronizing and thereby multiplexing a plurality ofbitstreams based on the sync data included in the caption data of thebitstream.

Effect of the Invention

According to embodiments of the present invention, by addingsynchronization data (sync data) to an ancillary data space included ina video signal, a decoding apparatus may synchronize imagescorresponding to the video signal without a need to transmit a separatesynchronization signal, or to perform a separate synchronizationprocess.

Also, according to embodiments of the present invention, by encodingsync data included in a video signal together with the video signal tothereby generate a bitstream, even though a plurality of bitstreams istransmitted without a synchronization process, a terminal receivingbitstreams may synchronize and play back the plurality of bitstreams.

Also, according to embodiments of the present invention, bitstreams tobe synchronized may be retrieved and thereby be synchronized based onsync data included in a bitstream. Accordingly, even though thebitstreams to be synchronized are not simultaneously received, it ispossible to retrieve and synchronize a bitstream to be synchronized fromamong initially received bitstreams.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a relationship between asynchronization data (sync data) adding apparatus and other apparatusesaccording to an embodiment of the present invention;

FIG. 2 is a block diagram illustrating a sync data adding apparatusaccording to an embodiment of the present invention;

FIG. 3 is a diagram illustrating an example of an ancillary data spaceto which a sync data adding apparatus adds sync data according to anembodiment of the present invention;

FIG. 4 is a block diagram illustrating an example of a system forencoding a video signal according to an embodiment of the presentinvention;

FIG. 5 is a block diagram illustrating an example of an encoding systemincluding a sync data adding apparatus according to an embodiment of thepresent invention;

FIG. 6 illustrates an example of top syntax of a bitstream generated byan encoding apparatus according to an embodiment of the presentinvention;

FIG. 7 illustrates an example of syntax capable of being inserted withancillary data in a bitstream generated by an encoding apparatusaccording to an embodiment of the present invention;

FIG. 8 illustrates an example of user data syntax associated with acaption in a bitstream generated by an encoding apparatus according toan embodiment of the present invention;

FIG. 9 is a block diagram illustrating an example of a binocularthree-dimensional (3D) television (TV) including a sync data addingapparatus according to an embodiment of the present invention; and

FIG. 10 is a flowchart illustrating a sync data adding method accordingto an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below in order to explain thepresent invention by referring to the figures. A synchronization data(sync data) adding method according to an embodiment of the presentinvention may be performed by a sync data adding apparatus.

FIG. 1 is a diagram illustrating an image obtaining system including async data adding apparatus according to an embodiment of the presentinvention.

Referring to FIG. 1, the image obtaining system may include a sync dataadding apparatus 100, a left camera 110, a left image recording medium115, a right camera 120, a right image recording medium 125, and asignal generating apparatus 130.

The left camera 110 may generate a first video signal that is a videosignal of a left image by photographing a left image of a photographingtarget, and may transmit the first video signal to the sync data addingapparatus 100.

The right camera 120 may generate a second video signal that is a videosignal of a right image by photographing a right image of thephotographing target, and may transmit the second video signal to thesync data adding apparatus 100.

Here, the left camera 110 and the right camera 120 may be gen-locked bythe signal generating apparatus 130, and may simultaneously transmit thefirst video signal and the second video signal based on asynchronization signal of the signal generating apparatus 130.

The sync data adding apparatus 100 may generate sync data, and may addthe sync data to an ancillary data space of the first video signal andan ancillary data space of the second video signal. Here, the sync datamay be information required to synchronize the left image and the rightimage such as a time code. Also, the ancillary data space may be one ofa vertical ancillary data space (VANC) positioned between video framesof the video signal and a data space for transmission at a verticalblanking interval (VBI).

Here, the sync data adding apparatus 100 may transmit the first videosignal and the second video signal in which the sync data is added, tothe left image recording medium 115 and the right image recording medium125, respectively, and thereby store the first video signal and thesecond video signal therein.

The sync data adding apparatus 100 may generate sync data using at leasta predetermined number of bits such as a time code that includes hourdata, minute data, and second data, and thereby prevent the samesynchronization signal from being overlappingly added in single videocontent or a connected video sequence.

Also, as shown in FIG. 1, the sync data adding apparatus 100 maygenerate sync data, and may add the sync data to ancillary data spacesof a plurality of video signals in all the interface standardsassociated with broadcasting and an image in addition to a video signalfor a three-dimensional (3D) image, and thereby enables the sync data tobe available as necessary. Here, the plurality of video signals to whichthe sync data adding apparatus 100 adds sync data may be video signalsof images that are associated with each other and thereby are requiredto be synchronized, such as a 3D image, a free-view image, a multi-viewimage, and images obtained by dividing a super resolution image.

That is, the sync data adding apparatus 100 may add sync data to anancillary data space included in a video signal. Through this, adecoding apparatus may synchronize images corresponding to the videosignal without a need to transmit a separate synchronization signal, orto performing a separate synchronization process.

FIG. 2 is a block diagram illustrating the sync data adding apparatus100 according to an embodiment of the present invention.

Referring to FIG. 2, the sync data adding apparatus 100 may include async data generator 210 and a sync data adder 220.

The sync data generator 210 may generate sync data by including a timecode based on a time when a video signal is received, or a playback timeof a video frame. Here, the sync data generator 210 may generate syncdata using at least a predetermined number of bits such as a time codethat includes hour data, minute data, and second data, and therebyprevent the same synchronization signal from being overlappingly addedin single video content or a connected video sequence.

The sync data adder 220 may add, to the ancillary data space of thevideo signal, the sync data that is generated by the sync data generator210. Here, the sync data adder 220 may determine, as the ancillary dataspace, one of a VANC, a data space for transmission at a VBI, and abancillary data space positioned between video frames of a video signalin national television system committee (NTSC), SD-serial digitalinterface (SDI), and HD-SDI standards, and may add sync data to the dataspace that is determined as the ancillary data space.

The ancillary data space will be further described with reference toFIG. 3.

FIG. 3 is a diagram illustrating an example of an ancillary data spaceto which a sync data adding apparatus adds sync data according to anembodiment of the present invention.

An image display apparatus may use a time for resetting or setting animage display function in order to display a subsequent screen afterdisplaying a single screen. Here, the image display apparatus may notuse the image display function and thus, a data received at the abovepoint in time may not be displayed on a screen.

Accordingly, as shown in FIG. 3, a video signal 300 of an image mayinclude an ancillary data space 330 between a first video frame 310 fordisplaying a single screen and a second video frame 320 for displaying asubsequent screen.

By adding sync data to the ancillary data space 330 included in thevideo signal 300, the sync data adding apparatus 100 may transmitinformation used to synchronize a video signal without a need totransmit a separate synchronization signal or additional information.

FIG. 4 is a block diagram illustrating an example of a system forencoding a video signal according to an embodiment of the presentinvention.

An encoding apparatus 410 may receive, from the left image recordingmedium 115, a first video signal in which sync data is added, and mayreceive, from the right image recording medium 125, a second videosignal in which sync data is added, and thereby encode the first videosignal and the second video signal based on a frame unit.

Specifically, the encoding apparatus 410 may identify the sync data inthe ancillary data space of the video signal, and may divide the videosignal based on a frame unit.

Next, the encoding apparatus 410 may generate a bitstream by encodingthe video signal divided based on the frame unit together with sync datacorresponding to a corresponding frame. Here, the encoding apparatus 410may store sync data in an elementary stream (ES) of a bitstream. Also,the encoding apparatus 410 may additionally define flag informationindicating whether sync data is present in a transport stream (TS)syntax, so that a multiplexing apparatus 420 may readily verify whetherthe sync data is present.

A next generation digital broadcasting, such as a 3DTV, a free viewbroadcasting, a multi-view broadcasting, a super resolution TV, and thelike, may need to maintain the compatibility with an existing desktopvideo (DTV) broadcasting.

That is, when at least one of a plurality of video signals is generatedas a bitstream according to an advanced television systems committee(ATSC) digital broadcasting standard used in the existing DTVbroadcasting, the encoding apparatus 410 may maintain the compatibilitywith the existing DTV broadcasting. A method of adding, by the encodingapparatus 410, sync data to a bitstream according to an ATSC digitalbroadcasting standard will be described with reference to FIGS. 6through 8.

The encoding apparatus 410 may transmit the generated bitstream to themultiplexing apparatus 420.

The encoding apparatus 410 may generate a bitstream by encoding a videosignal and sync data included in the video signal. Through this, withouta need to synchronize and multiplex bitstreams using the multiplexingapparatus 420, a terminal receiving a bitstream may synchronize andthereby play back the plurality of bitstreams. For example, as in anon-real time (NRT) 3D broadcasting, even though a left image signal anda right image signal are separately transmitted without beingmultiplexed, a terminal receiving a signal may synchronize and therebyplay back the left image signal and the right image signal using syncdata included in the signals.

The multiplexing apparatus 420 may synchronize and thereby multiplex aplurality of bitstreams based on sync data that is included in abitstream received from the encoding apparatus 410.

Specifically, the multiplexing apparatus 420 may identify sync data ofeach frame by interpreting an ES syntax of the bitstream that isreceived from the encoding apparatus 410.

Next, the multiplexing apparatus 420 may search for a frame of anotherbitstream having the same sync data as the identified sync data.

Next, the multiplexing apparatus 420 may synchronize a frame of thebitstream retrieved based on the sync data with a frame of the receivedbitstream.

The multiplexing apparatus 420 may multiplex and thereby output thesynchronized bitstreams.

A conventional multiplexing apparatus needs to receive bitstreams thatare to be synchronized and be multiplexed at the same time and thus, thenumber of encoding apparatuses corresponding to the number of bitstreamsto be multiplexed may be required. For example, as shown in FIG. 4, tomultiplex bitstreams in which a left image and a right image areencoded, respectively, the left image and the right image may besimultaneously encoded using two encoding apparatuses, and the bitstreamof the left image and the bitstream of the right image may need to bereceived from the two encoding apparatuses and be multiplexed at thesame time.

On the other hand, the multiplexing apparatus 420 according to thepresent invention may need to search for and synchronize bitstreams tobe synchronized based on sync data included in a bitstream. Accordingly,even though bitstreams to be synchronized are not received at the sametime, the encoding apparatus 420 may search for and thereby multiplex abitstream having the same bit data from among initially receivedbitstreams. Accordingly, regardless of the number of encodingapparatuses, the multiplexing apparatus 420 according to the presentinvention may synchronize and multiplex a plurality of bitstreams.

For example, as shown in FIG. 4, the multiplexing apparatus 420 maygenerate a plurality of bitstreams by sequentially encoding a pluralityof video signals using a single encoding apparatus 410, and may storebitstreams that are received from the encoding apparatus 410. Whenencoding of the images is completed, the multiplexing apparatus 420 maysynchronize the plurality of stored bitstreams using sync data that isincluded in the plurality of bitstreams.

Also, a decoding apparatus according to the present invention may decodea received bitstream, and may synchronize the decoded bitstream usingthe same method as the multiplexing apparatus 420.

Specifically, the decoding apparatus may identify sync data of eachframe by interpreting an ES syntax of the decoded bitstream.

Next, the decoding apparatus may search for a frame of another bitstreamhaving the same sync data as the identified sync data.

Next, the decoding apparatus may synchronize a frame of the bitstreamretrieved based on the sync data with a frame of the received bitstream.

FIG. 5 is a block diagram illustrating an example of an encoding systemincluding a sync data adding apparatus according to an embodiment of thepresent invention.

Referring to FIG. 5, the encoding system may include a sync data addingapparatus 100, a left camera 110, a right camera 120, a signalgenerating apparatus 130, a first encoding apparatus 510, a secondencoding apparatus 520, and a multiplexing apparatus 530. Here, the leftcamera 110, the right camera 120, and the signal generating apparatus130 may perform the same functionality as described above with referenceto FIG. 1 and thus, a further detailed description will be omitted here.

The sync data adding apparatus 100 may generate sync data, may add thesync data to an ancillary data space of a first video signal that isreceived from the left camera 110, and may transmit the first videosignal to the first encoding apparatus 510. Also, the sync data addingapparatus 100 may add the sync data to an ancillary data space of asecond video signal that is received from the right camera 120, and maytransmit the second video signal to the second encoding apparatus 520.

The first encoding apparatus 510 may generate a first bitstream byencoding, based on a frame unit, the first video signal that is receivedfrom the sync data adding apparatus 100. Here, the first encodingapparatus 510 may identify the sync data from the ancillary data spaceof the first video signal, and may add the identified sync data to auser data syntax among syntaxes of the first bitstream. The firstencoding apparatus 510 may transmit, to the multiplexing apparatus 530,the first bitstream in which the sync data is added.

The second encoding apparatus 520 may generate a second bitstream byencoding, based on a frame unit, the second video signal that isreceived from the sync data adding apparatus 100. Here, the secondencoding apparatus 520 may identify the sync data from the ancillarydata space of the second video signal, and may add the identified syncdata to, a user data syntax among syntaxes of the second bitstream. Thesecond encoding apparatus 520 may transmit, to the multiplexingapparatus 530, the second bitstream in which the sync data is added.

The multiplexing apparatus 530 may synchronize and multiplex a frame inwhich the same sync data is added to the first bitstream and the secondbitstream, based on the sync data that is included in each of the firstbitstream and the second bitstream.

FIG. 6 illustrates an example of top syntax of a bitstream generated byan encoding apparatus according to an embodiment of the presentinvention.

An ATSC digital broadcasting standard encodes a video signal using anMPEG-2 video encoding standard. Therefore, video sequence( ) that is atop syntax of MPEG-2 bitstream generated by the encoding apparatus 410according to the ATSC digital broadcasting standard may includeextension_and_user_data(2) 610.

Also, the encoding apparatus 410 may include extension_and_user_data(1)in video sequence( ), instead of including extension_and_user_data(2)610.

Here, in extension_and_user_data(1), ancillary data may be insertedbased on a group of pictures (GOP). In extension_and_user_data(2),ancillary data may be inserted into an encoded bitstream based on apicture unit. Also, the GOP unit may include an encoded picture of aplurality of frames and thus, be a randomly accessible independentencoding unit. The picture may be an image in which each video frame isencoded. A plurality of frames corresponding to the GOP unit may includeframes from a single key frame to a subsequent key frame.

As shown in FIG. 7, extension_and_user_data(1) orextension_and_user_data(2) may include user_data( ) 710. Here, in FIG.7, i may be either 1 or 2.

The encoding apparatus 410 may store sync data in user_data( ) 710 thatis included in extension_and_user_data(1) or extension_and_user_data(2).

For example, when the sync data adding apparatus 100 generates sync datausing a time code that is indicated as hour, minute, second, and thenumber of frames, the encoding apparatus 410 may store sync data inuser_data( ) 710 based on a time code syntax according to society ofmotion picture and television engineers (SMPTE) 334-2: captiondistribution packet definition standard, as shown in the following Table1:

TABLE 1 Syntax Bits Meaning time_code( ){ tc_10hrs 2 Value of ten hourunit tc_1hrs 4 value of one hour unit Reserved 1 ‘1’ tc_10min 3 Value often minute unit tc_1min 4 Value of one minute unit tc_feld_flag 1 In aninterlace picture, set as zero if it is a first field, and set as ‘1’ ifit is a second filed. In a progressive picture, used for counting thenumber of frames. That is, interpreted as (2*frame + flag). tc_10sec 3Value of ten minute second tc_1sec 4 Value of one minute seconddrop_frame_flag 1 When time code count compensates for drop-frame, it isindicated as 1 and otherwise, it is indicated as zero. zero 1 ‘0’tc_10fr 3 Counted value of ten frame unit tc_1fr 4 Counted value of oneframe unit. } }

When the multiplexing apparatus 420 multiplexes, to a single MPEG-2 TS,bitstreams that are received from the plurality of encoding apparatuses410, or bitstreams that are received from a single encoding apparatus410, the multiplexing apparatus 420 may multiplex the bitstreams usingsync data that is stored in user_data( ) 710.

Here, the multiplexing apparatus 420 may determine an interval forverifying sync data based on the user data syntax in which the sync datais added, and may synchronize the plurality of bitstreams by verifyingthe sync data at the determined intervals. For example, when the syncdata is stored in user_data( ) 710 of extension_and_user_data(1), themultiplexing apparatus 420 may perform multiplexing by verifying thesync data based on a GOP unit. Also, when the sync data is stored inuser_data( ) 710 of extension_and_user_data(2), the multiplexingapparatus 420 may perform multiplexing by verifying the sync data basedon a picture unit.

Also, extension_and_user_data(1) or extension_and_user_data(2) may be asyntax for storing ancillary data instead of image information.Accordingly, even though a decoding apparatus that receives and decodesa signal output from the multiplexing apparatus 420 is incapable ofinterpreting the sync data that is stored in user_data( ) 710 ofextension_and_user_data(2), the decoding apparatus may restore an imageby decoding the syntax in which the image information is encoded. Thatis, even a conventional decoding apparatus incapable of identifying syncdata may restore an image of an encoded signal according to the presentinvention and thus, the encoding system according to the presentinvention may be compatible with the conventional decoding apparatus.

FIG. 8 illustrates an example of user data syntax associated with acaption in a bitstream generated by an encoding apparatus according toan embodiment of the present invention.

An ATSC digital broadcasting standard defines a picture user data syntaxthat indicates closed caption data or bar data in user_data( ) of anMPEG-2 video encoded bitstream.

The encoding apparatus 410 according to the present invention maytransmit sync data according to the ATSC digital broadcasting standardby adding time code( ) 810 of table 1 to picture user data syntax ofuser data( ) 710. Here, a syntax 820 associated with user_data_type_codemay be one of ATSC_reserved_user_data, and may be a conditional syntaxfor identifying time code( ) 810.

FIG. 9 is a block diagram illustrating an example of a binocular 3DTVtransmitting system that includes a caption data adding apparatusaccording to an embodiment of the present invention.

FIG. 9 shows an example in which a sync data adding function accordingto an embodiment of the present invention is added to the caption dataadding apparatus of the binocular 3DTV transmitting system based on aconventional MPEG-2 encoding apparatus and a heterogeneous codecencoding apparatus. Here, a left camera 110, a right camera 120, and asignal generating apparatus 130 may perform the same functionality asdescribed above with reference to FIG. 1 and thus, a further detaileddescription will be omitted here.

A caption data adding apparatus 900 may generate sync data and captiondata associated with an image photographed from the left camera 110 andthe right camera 120, and may add the caption data including the syncdata to an ancillary data space of a first video signal and an ancillarydata space of a second video signal. Here, the caption data addingapparatus 900 may generate caption data, for example, closed captionusing SMPTE 333M or SMPTE 334M that are standards with respect toEIA-608 (analog and SD-SDI closed captioning) and EIA-708 (HD-SDI closedcaptioning).

An MPEG-2 encoding apparatus 910 may encode caption data together with avideo signal, and may output the same to an MPEG-2 TS.

Here, the MPEG-2 encoding apparatus 910 may not generate a bitstream byinserting sync data in user_data( ) within extension_and_user_data(1) orextension_and_user_data(2). Accordingly, the MPEG-2 encoding apparatus910 may store the sync data by adding time code( ) 810 to cc_data( )that indicates a position of caption broadcasting data pair.

When using an MPEG-2 encoding method, the video encoding apparatus 920may encode the video signal and the caption and thereby output the sameto an MPEG-2 TS. Here, the video encoding apparatus 920 may store thesync data by adding time code( ) 810 to cc_data( ).

Also, when using an advanced video coding (AVC) or high efficiency videocoding (HEVC) based encoding method, the video encoding apparatus 920may generate a bitstream by encoding caption data based on a frame unit.Here, the video encoding apparatus 920 may identify the sync data fromthe ancillary data space of the second video signal, and may add theidentified sync data to a user data syntax among syntaxes of the secondbitstream. The video encoding apparatus 920 may transmit, to themultiplexing apparatus 930, the bitstream in which the sync data isadded.

The multiplexing apparatus 930 may identify sync data of each frame byverifying cc_data( ) of MPEG-2 TS that is received from the MPEG-2encoding apparatus 910 and user_data( ) of a bitstream that is receivedfrom the video encoding apparatus 920, and may synchronize and therebymultiplex the MPEG-2 TS received from the MPEG-2 encoding apparatus 910and the bitstream received from the video encoding apparatus 920.Through this, the multiplexing apparatus 930 may generate and output anMPEG-2 3D TV TS signal about 3D TV broadcasting content.

FIG. 10 is a flowchart illustrating a sync data adding method accordingto an embodiment of the present invention.

In operation S1010, the sync data adding apparatus 100 may generate syncdata including a time code based on a time when a video signal isreceived, or a playback time of a video frame.

In operation S1020, the sync data adding apparatus 100 may add thegenerated sync data to an ancillary data space of the video signal.

In operation S1030, the sync data adding apparatus 100 may generate abitstream by encoding the video signal in which the sync data is added,based on a frame unit.

Specifically, the encoding apparatus 410 may generate a bitstream byidentifying the sync data from the ancillary data space of the videosignal, and by encoding the video signal divided based on a frame unittogether with sync data corresponding to a corresponding frame.

In operation S1040, the multiplexing apparatus 420 may synchronize andthereby multiplex a plurality of bitstreams based on the sync data thatis included in the bitstream generated in operation S1030.

Specifically, in operation S1030, the multiplexing apparatus 420 mayidentify sync data of a bitstream and may search for another bitstreamhaving the same sync data as the identified sync data. Next, themultiplexing apparatus 420 may synchronize and thereby multiplex a frameof the bitstream retrieved based on the sync data with a frame of thebitstream generated in operation S1020.

According to embodiments of the present invention, by adding sync datain an ancillary data space of a video signal, a decoding apparatus maysynchronize images corresponding to the video signal without a need totransmit a separate synchronization signal or performing a separatesynchronization process.

According to embodiments of the present invention, it is possible togenerate a bitstream by encoding a video signal and sync data includedin the video signal. Therefore, even though a plurality of bitstreams istransmitted without a synchronization process, a terminal receiving thebitstream may synchronize and play back the plurality of bitstreams.

According to embodiments of the present invention, bitstreams to besynchronized may be retrieved and be synchronized based on sync dataincluded in a bitstream. Accordingly, even though bitstreams to besynchronized are not simultaneously received, it is possible to retrieveand synchronize a bitstream to be synchronized among initially receivedbitstreams.

Although a few embodiments of the present invention have been shown anddescribed, the present invention is not limited to the describedembodiments. Instead, it would be appreciated by those skilled in theart that changes may be made to these embodiments without departing fromthe principles and spirit of the invention, the scope of which isdefined by the claims and their equivalents.

The invention claimed is:
 1. An encoding system, comprising: a sync dataadding apparatus to add sync data to an ancillary data space of a videosignal; an encoding apparatus to generate a bitstream in which the syncdata is added by encoding the video signal in which the synch data isadded; and a multiplexing apparatus to synchronize a plurality ofbitstreams based on the sync data included in the bitstream, andmultiplexes the synchronized bitstreams, wherein the encoding apparatusidentifies the sync data in the ancillary data space of the videosignal, and adds the identified sync data to a user data syntax amongsyntaxes of the bitstream, and wherein the multiplexing apparatusdetermines an interval for verifying the sync data based on the userdata syntax added with the sync data, and synchronizes the plurality ofbitstreams by verifying the sync data at the determined intervals.
 2. Anencoding method, comprising: adding sync data related to timeinformation to an ancillary data space of a video signal; and generatingan MPEG-2 bitstream by encoding the video data using MPEG-2 videoencoding scheme, wherein the MPEG-2 bitstream includes video sequence( )syntax, wherein the video sequence( ) syntax includes the ancillary datacorresponding to extension_and_user_data( ) syntax inserted in theMPEG-2 bitstream, based on a group of pictures (GOP) of the video data,or a picture unit.
 3. An encoding method, comprising: adding sync datato an ancillary data space of a video signal; generating a bitstream inwhich the sync data is added by encoding the video signal in which thesynch data is added; synchronizing a plurality of bitstreams based onthe sync data included in the bitstream; and multiplexing thesynchronized bitstreams, wherein the generating comprises identifyingthe sync data in the ancillary data space of the video signal, andadding the identified sync data to a user data syntax among syntaxes ofthe bitstream, and wherein the synchronizing comprises determining aninterval for verifying the sync data based on the user data syntax addedwith the sync data, and synchronizing the plurality of bitstreams byverifying the sync data at the determined intervals.